Abstract: Cloud computing has been widely applied in many fields with the development of internet technology, in which data integrity techniques play an important role. However, there are few effective approaches to analyze and verify the data integrity. In this paper, by combining the advantage of PoR(Proof of Retrievability) and MD5(Message Digest), a new approach to verifying the integrity of the cloud stored data is proposed, in which the technologies, such as data block, random sampling and periodic verification are used. It is shown from real implementation and analysis results that the proposed method can effectively verify the data integrity of cloud stored data and improve the security of cloud computing.